The plant and faunal species composition and diversity on rooftop farms: Seasonal variation and the effects of site and surrounding characteristics

Abstract

The importance of human-dominated green spaces for biodiversity support is increasing. With the popularity of rooftop farms to grow healthy and local food, can rooftop farms provide wildlife habitats? This study conducted a year-round survey on eight rooftop farms to reveal (1) plant and faunal species composition and diversity of the rooftop farms, (2) variations in plant and faunal species composition by site and the four seasons, (3) effects of site and surrounding characteristics on faunal species composition and diversity, and (4) examine whether higher taxa was adequate in indicating species-level faunal species composition on rooftop farms. This study used visual observation and pitfall trap methods to conduct a faunal species survey twice a season; and recorded plant species and their blooming status in each survey. Arthropods were the survey target, and Molluscs found in the cultivation area were also recorded. The season averages in plant species number and blooming species were 30–50% and 20–30% of the total number of plant species in a year. Generalist species dominated rooftop farms. Site and seasons significantly affected faunal species composition and diversity. The site characteristics significantly affected the rooftop farms' faunal species composition and diversity, but the surrounding characteristics almost had no effects. The larger rooftop area led to a larger cultivation area, resulting in more plant and blooming species and attracting more faunal species. Humans managed the vegetation on the rooftop farms might form a distinct habitat. Family-level performed well as a surrogate in indicating faunal species-level composition on rooftop farms.